| As the modern architectural engineering tends to be super height,heavy load,large span and giant,conventional architectural material and structure forms can no longer adapt to the requirements of this development.Therefore,based on the structures of steel reinforced concrete and concrete filled steel tube,this paper fully utilizes the concept of “combination” and structures the strength-gradient composite columns with built-in high-strength concrete filled steel tube(SGCC),which are centered on high strength concrete filled steel tube and wrapped with reinforced concrete.SGCCs not only inherit the advantages of traditional concrete filled steel tube columns,but also upgrade bearing capacity,deformation capacity,fire resistance,durability and e economical efficiency due to the reinforced concrete wrapped out.In recent years,Domestic and foreign scholars has carried out several researches on the mechanical property of steel tube-reinforced concrete columns,however,researches on the axial compression and seismic behavior of strength-gradient components proposed in this paper are relatively few.Through the combination of experimental research,simulation analysis and theoretical analysis,detailed researches on the axial compression and seismic performance of SGCCs have been carried out in this paper,the main research contents are as follows:(1)First of all,domestic and foreign researches related to SGCCs have been systematically reviewed and comprehensively comprehended in this paper,which will established the foundation of further researches.(2)Text of 10 short SGCCs under axial compression has been carried out in this paper,of which the main parameters are shear span ratio,confinement index and stirrup ratio of outer-concrete.Then the destruction form,the whole process curve of N-Δ,and development of strain within the same section are acquired based on the results of text,which helps to investigate the influence of different control parameters on the bearing capacity and ductility of specimens.The research results indicate that all destructive phenomenon shares a same sign of transfixion between middle cracks and end cracks;research results also indicates shear span ratio and stirrup ratio are the main parameters which influences the axial compression bearing capacity and ductility of specimens.(3)The finite element models of SGCCs are established based on the suitable material constitutive model and reasonable modeling method,then the simulation results were compared with text data in order to verify the rationality of finite element model established before.Furthermore,the axial compression performance simulation of 36 SGCCs are carried out,destructive form,stress and strain distribution and internal working mechanism are focused in the whole analysis process.At last,the simplified computing formula of axial compressive capacity of SGCCs was also proposed based on the superposition principle.(4)The pseudo-static simulation analysis of 13 SGCCs have been carried out afterwards,of which the main parameters are assigned as strength of concrete inside and outside the steel tube,confinement indice,stirrup characteristic value,axial compression ratio and HSCFST ratio respectively.Then investigates the change rules of energy dissipation coefficient,strength degradation,secant stiffness,skeleton curves and ductility by six main parameters based on text data.The research results indicate that the energy dissipation coefficients are all above 1.5,the energy dissipation of SGCCs is between reinforced concrete columns and steel reinforced concrete columns;the ductility coefficients of SGCCs are all above 4.When the axial compression ratio of SGCCs maintain invariant,improving the stirrup characteristic value within certain range will improve the energy dissipation capacity of specimens,reduce the degradation rate of strength and stiffness,and also improve the deformation capacity of specimens. |
